Method for twisting a hollow metal tube

ABSTRACT

A method for twisting a hollow metal tube includes the steps of (a) filling a predetermined section of the hollow metal tube between two opposite end sections of the hollow metal tube with a solid reinforcing member, and (b) holding and turning the two opposite end sections of the hollow metal tube relative to each other so as to twist the predetermined section of the hollow metal tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for twisting a tube, more particularly to a method for twisting a hollow metal tube which is simple and easy to implement.

2. Description of the Related Art

Referring to FIGS. 1, 2 and 3, a conventional method for twisting a hollow metal tube includes the steps of a) preparing a hollow metal tube 1; b) installing a pressure adjusting device 2 (i.e., a fluid controlling valve) at an open end of the metal tube 1; c) filling a support fluid 3 into the metal tube 1 through the pressure adjusting device 2, and keeping the pressure of the support fluid 3 above a predetermined value; d) holding and turning predetermined end portions of the metal tube 1 relative to each other so as to twist the metal tube 2 to form the surface of the metal tube 2 with a twisted structure 101; and e) releasing the support fluid 3 through the pressure adjusting device 2.

Although the aforesaid conventional method can be used to make a twisted metal tube, the conventional method has the following shortcomings:

1. The pressure adjusting device 2 is required to keep the, pressure of the support fluid 3 above a predetermined value, which is troublesome and which is inconvenient for the operation of holding and turning the metal tube 1.

2. Since the support fluid 3 is used in the conventional method, a good leak-proof effect is required for both the metal tube 1 and the pressure adjusting device 2. For example, when the metal tube 1 has two open end portions, an additional leak-proof treatment is required for the end portion without the pressure adjusting device 2. Therefore, the conventional method is relatively complicated to implement.

3. The amount of the support fluid 3 varies according to the length of the metal tube 1 to be treated. Therefore, when the length of the metal tube 1 is increased, the amount of the support fluid 3 should be increased as well so as to provide a sufficient support for the metal tube 1.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for twisting a hollow metal tube which is relatively simple and easy to implement, and which can overcome the aforesaid disadvantages of the prior art.

Accordingly, a method for twisting a hollow metal tube of this invention includes the steps of:

(a) filling a predetermined section of the hollow metal tube between two opposite end sections of the hollow metal tube with a solid reinforcing member, said solid reinforcing member filling said predetermined section of said hollow metal tube and further extending into said opposite end sections of said hollow metal tube; and

(b) holding and turning the two opposite end sections of the hollow metal tube relative to each other so as to twist the predetermined section of the hollow metal tube.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:

FIG. 1 is a flow diagram of a conventional method for twisting a hollow metal tube;

FIG. 2 is a fragmentary sectional view showing how the conventional method is conducted;

FIG. 3 is a perspective view of a twisted hollow metal tube made by the conventional method;

FIG. 4 is a flow diagram of the first preferred embodiment of a method for twisting a hollow metal tube according to this invention;

FIGS. 5 to 8 are views showing consecutive steps of the first preferred embodiment;

FIG. 9 is a perspective view of a twisted hollow metal tube made by the first preferred embodiment;

FIG. 10 is a perspective view of another twisted hollow metal tube made by the first preferred embodiment; and

FIGS. 11 and 12 are views showing some steps of the second preferred embodiment of a method for twisting a metal hollow tube according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the present invention is described in greater detail, it should be noted that like elements are denoted by the same reference disclosure.

Referring to FIG. 4, the first preferred embodiment of the method for twisting a hollow metal tube according to this invention includes the following steps:

A) Filling:

Referring to FIGS. 5 and 6, a hollow metal tube 10 and a solid reinforcing member 20 are prepared. The hollow metal tube 10 has opposite first and second end sections 11, 12 and a predetermined section 13 between the first and second end sections 11, 12 and extending along an axial direction (x). The first and second end sections 11, 12 define first and second holes 111, 121, respectively. The predetermined section 13 defines an intermediate channel 131 communicated with the first and second holes 111, 121 and having a length (L1) along the axial direction (x). The hollow metal tube 10 used in the preferred embodiment has a Vickers-hardness (Hv) between 210 and 270. The first hole 111, the second hole 121, and the intermediate channel 131 of the hollow metal tube 10 are identical to each other in cross-section shape, which corresponds to that of the solid reinforcing member 20. The solid reinforcing member 20 has a length (L2) longer than the length (L1) of the intermediate channel 131. The solid reinforcing member 20 used in the preferred embodiment is a plastic material having a Vickers-hardness not less than 60. The solid reinforcing member 20 fills the intermediate channel 131 of the predetermined section 13 of the hollow metal tube 10 through the first hole 111 or the second hole 121, and further extends into the first and second holes 111, 121 of the first and second end sections 11, 12 so as to provide the predetermined section 13 of the hollow metal tube 10 with a sufficient support for the subsequent processing.

B) Holding and Turning:

Referring to FIGS. 7 and 8, the opposite first and second end sections 11, 12 of the hollow metal tube 10 are held by first and second holders 31, 32 of a known twisting device 30, and are turned relative to each other so as to twist the predetermined section 13 of the hollow metal tube 10 to form a twisted structure 132.

C) Removing:

Optionally, the hollow metal tube 10, after the step B), can be heated to melt the solid reinforcing member 20, thereby enabling removal of the melted reinforcing member from the hollow metal tube 10 by flowing through the first hole 111 or the second hole 121 of the hollow metal tube 10. Referring to FIG. 9, the hollow metal tube 10 provided with the twisted structure 131 can be obtained accordingly.

Referring to FIG. 10, the hollow metal tube 10 can be formed with a plurality of twisted structures 132 through the aforesaid preferred embodiment.

In view of the aforesaid, the method of this invention has the following advantages:

1. Since the solid reinforcing member 20 is used for supporting the predetermined section 13 of the hollow metal tube 10 during the holding and turning of the hollow metal tube 10, the pressure adjusting device 2 required in the prior art can be eliminated. Therefore, the holding and turning operation for the hollow metal tube 10 is simplified, and the method of this invention is thus more convenient to conduct as compared to the prior art in which the support fluid 3 is used.

2. The leaking problem which may be encountered in the prior art can be avoided by using the solid reinforcing member 20 in the method of this invention.

3. The position of the solid reinforcing member 20 in the hollow metal tube 10 can be adjusted easily, such that a plurality of twisted structures 132 can be formed on the hollow metal tube 10, as shown in FIG. 10.

Notably, as described above, the step C) of removing the solid reinforcing member 20 is optional. In other words, the solid reinforcing member 20 can remain in the hollow metal tube 10 after turning the hollow metal tube 10. Therefore, in addition to the plastic material, other materials such as metal, wood, and the like can be used as the solid reinforcing member 20.

Referring to FIGS. 11, and 12, the second preferred embodiment of the method of this invention is shown to be similar to the first preferred embodiment, except that the second preferred embodiment further includes a step of forging the predetermined section 13 of the hollow metal tube 10 and the solid reinforcing member 20 by a forging device 40 between the step (a) and the step (b) of the first preferred embodiment. The cross-section of the predetermined section 13 of the hollow metal tube 10 is reduced after the step of forging. Additionally, a textured pattern can be formed on the hollow metal tube 10 by the step of forging. In the second preferred embodiment, the solid reinforcing member 20 and the hollow metal tube 10 are made of the same material.

While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

1. A method for twisting a hollow metal tube, comprising the steps of: a) filling a predetermined section of said hollow metal tube between two opposite end sections of said hollow metal tube with a solid reinforcing member, said solid reinforcing member filling said predetermined section of said hollow metal tube and further extending into said opposite end sections of said hollow metal tube; and (b) holding and turning said two opposite end sections of said hollow metal tube relative to each other so as to twist said predetermined section of said hollow metal tube.
 2. The method as claimed in claim 1, further comprising a step (c) of removing said solid reinforcing member from said hollow metal tube after the step (b).
 3. The method as claimed in claim 2, wherein said solid reinforcing member is a material having a melting point lower than that of said hollow metal tube, the step (c) being conducted by melting said solid reinforcing member so as to enable said melted reinforcing member to flow out of said hollow metal tube.
 4. The method as claimed in claim 3, wherein said solid reinforcing member has a Vickers-hardness not less than
 60. 5. The method as claimed in claim 3, wherein said solid reinforcing member is a plastic material.
 6. The method as claimed in claim 1, further comprising a step of forging said predetermined section of said hollow metal tube and said solid reinforcing member between the step (a) and the step (b), wherein said solid reinforcing member and said hollow metal tube are made of the same material.
 7. The method as claimed in claim 6, wherein the cross-section of said predetermined section of said hollow metal tube is reduced after the step of forging. 